Simultaneous Determination of Loratadine and Preservatives in Syrups by Thin-layer Chromatography

Simple, rapid, and precise densitometric TLC methods have been established for simultaneous determination of loratadine and preservatives in loratadine–sodium benzoate and loratadine–methylparaben–propylparaben mixtures. Chromatography was performed on aluminium plates precoated with silica gel 60 F254. The mobile phases were n-butyl acetate–carbon tetrachloride–acetic acid–acetonitrile 3:6:0.2:3 (v/v) for loratadine–sodium benzoate mixtures and ethyl acetate–n-hexane–methanol–ammonia– diethylamine 1:4:0.8:0.4:2 (v/v) for loratadine–methylparaben–propylparaben mixtures. Chromatographic zones were scanned in reflectance–absorbance mode at 240 nm for the former mixture and 275 nm for the latter. Relationships between peak areas and amounts of the compounds were evaluated by linear regression analysis in the concentration ranges 0.3–0.7 μg per band for loratadine, methylparaben, and sodium benzoate and 0.03– 0.07 μg per band for propylparaben. Mean recovery for all the compounds varied from 98.3 to 102.5 %. Detection and quantification limits ranged from 0.004 to 0.03 and from 0.01 to 0.1 μg per band, respectively. The proposed method was used for simultaneous determination of loratadine and the preservatives in commercial medicinal syrups.